Domestic Hot Water Boilers
SUGGESTED SPECIFICATION
The hot water supply boiler(s) shall be A. O. Smith Dura-Max® model DW ______ with an input rating of ______ BTU/hr and a recovery rating of ________________ BTU/hr at
100°F temperature rise. The boiler(s) shall be design-tested and certified to the ANSI Z21.13 standard, approved by CSA International and shall carry the ASME “H” Symbol. The wet
section shall be design-registered in accordance with the requirements of the ASME Code and shall carry an appropriate National Board Number or Canadian Registration Number.
All waterways shall be copper, brass or bronze. The heat exchanger shall be a two (2)-pass design incorporating integral-finned copper tubes. The double-row heat exchanger
shall have staggered tubes. Cast bronze return bends shall be readily removable to permit visual inspection or cleaning without removing the entire wet section assembly. Silicone
“O”-ring gaskets shall form a water-tight seal by compression and shall be isolated from the flue gases by 3/4” board-type ceramic fiber insulation. The heat exchanger assembly
shall be hydrostatically tested to a pressure of 240 psi (1655 kPa) and shall have a maximum working pressure of 160 psi (1100 kPa).The combustion chamber shall be constructed
of board-type ceramic fiber insulation rated to 2300°F (1260°C) which interlocks to form a gas-tight seal and shall be supported in a heavy-gauge corrugated steel frame. The
external cabinet shall incorporate a built-in draft hood and shall be of baked enamel steel construction. It shall be suitable for installation on combustible flooring. The burners
shall be a stainless steel stamped design and shall be mounted in a removable drawer assembly.The burner controls shall be 24 VAC and shall include slow-opening main gas valve
for soft ignition, redundant safety shutoff gas valve, main and pilot pressure regulators, recycling intermittent pilot system with one-second shutdown in the event of pilot flame
failure, automatic recycling high limit, manual reset ECO limit, main and pilot manual cocks and manual firing valve, and an ASME-rated pressure relief valve. The boiler shall be
approved by Factory Mutual (FM).The boiler shall comply with current edition ASHRAE/IESNA 90.1. Optional: Factory-installed, dial-type temperature and pressure gauges shall
be mounted on the front of the cabinet.
For Technical Information and Automated Fax Service, call 800-527-1953. A.O. Smith Corporation reserves the right to make product changes or improvements without prior notice.
Revised November 2009
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